The present invention relates to a pressure-sensitive barrier tape construction particularly suited as a barrier for covering the vents or ports provided in a cavity to be filled with a thermally insulating or cushioning foam such as a urethane foam. The barrier tape comprises a thin, porous, nonwoven web unified by being coated with a pressure-sensitive adhesive resin which substantially coats the fibers thus bonding them together at their crossing points while leaving the interstices of the web unfilled.
The widespread use of rigid urethane foam for thermal insulation in such applications as household refrigerators and freezers, trailer bodies, railroad cars, construction and industrial insulation results perhaps as much from its low moisture permeability and low water absorption characteristics as well as from its insulating qualities.
The "one-shot" method of foaming through the use of modified toluene diisocyanate has greatly simplified the foam application process and the reaction mixture is generally of lower viscosity with improved mixability and flow. These characteristics are most desirable for the filling of complex shapes since the mixture can readily flow and fill the cavity as the foaming takes place.
In addition to its thermal insulating properties, urethane foam, in its flexible form, provides superior cushioning properties in such areas as chair cushions, automotive seats, and molded furniture.
In all of these uses, the air in the empty cavity must be displaced and the volume completely and uniformly filled with foam. The foaming process liberates dissolved gases such as carbon dioxide or fluorocarbons as well as other gaseous reaction products. These gases are forced through small vents or ports provided in the walls of the cavity as the foam expands.
It will be realized, of course, that in addition to the gases, fluid foam can also escape through these vents. This results in unnecessary waste of materials and creates the need to remove, by cutting, the exuded bumps of foam extending through the vents or ports. The open cut surface of the foam must then be sealed as by brushing on of a solvent to prevent the entrance of unwanted moisture into the foam.
Prior to this invention, a type of foam barrier was made by forming pads of 1/2 inch thick fiberglass insulation, applying a rubber cement to the surface surrounding the vent, and gluing the pads in place over the vents. These barriers, in addition to being hazardous to the health, were ofttimes ineffective and exuded foam still had to be cut from the wall surface and the cut then sealed to prevent moisture intrusion into the foam or if the resistance were too great, then adequate escape of the gases cannot occur and the cavity would not be uniformly filled with foam and the insulating value of the cabinet reduced.
The present invention provides a simple barrier means that is gas-permeable, urethane foam-impermeable and which is self-adhesively applied to the interior wall of a cavity to be filled with urethane foam, so as to cover the vents, thus allowing the cavity to be uniformly filled with foam while preventing the escape of foam therefrom.